A battery includes a positive electrode including a positive electrode active material, a negative electrode, and an electrolytic solution including a nonaqueous solvent. The positive electrode active material includes a compound having a crystal structure belonging to a space group FM3-M and represented by Compositional Formula (1): Li.sub.xMe.sub.yO.sub.αF.sub.β, where, Me is one or more elements selected from the group consisting of Mn, Co, Ni, Fe, Al, B, Ce, Si, Zr, Nb, Pr, Ti, W, Ge, Mo, Sn, Bi, Cu, Mg, Ca, Ba, Sr, Y, Zn, Ga, Er, La, Sm, Yb, V, and Cr; and subscripts x, y, α, and β satisfy the following requirements: 1.7≤x≤2.2, 0.8≤y≤1.3, 1≤α≤2.5, and 0.5≤β≤2. The nonaqueous solvent includes a solvent having at least one fluoro group.

The present invention provides an active electrode material comprising a mixture of (a) at least one niobium oxide and (b) at least one mixed niobium oxide; wherein the mixed niobium oxide has the composition M1.sub.aM2.sub.1-aM3.sub.bNb.sub.12-bO.sub.33-c-dQ.sub.d, wherein: M1 and M2 are different; M1 is selected from Mg, Ca, Sr, Y, La, Ce, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Zn, Cd, B, Al, Ga, In, Si, Ge, Sn, Pb, P, Sb, Bi and mixtures thereof; M2 is Mo or W; M3 is selected from Mg, Ca, Sr, Y, La, Ce, Ti, Zr, Hf, V, Ta, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Zn, Cd, B, Al, Ga, In, Si, Ge, Sn, Pb, P, Sb, Bi, and mixtures thereof; Q is selected from F, Cl, Br, I, N, S, Se, and mixtures thereof; 0≤a<0.5; 0≤b≤2; −0.5≤c≤1.65; 0≤d≤1.65; one or more of a, b, c and d does not equal zero; and when a, b, and d equal zero, c is greater than zero. Such materials are of interest as active electrode materials in lithium-ion or sodium-ion batteries.

A cathode including: a cathode current collector; and a cathode active material layer disposed on the cathode current collector and including a first surface, and a second surface opposite the first surface and adjacent to the cathode current collector, wherein the cathode active material layer includes a cathode active material including a dopant, and wherein a concentration gradient of the dopant decreases in a direction from the first surface to the second surface.

A cathode including: a cathode current collector; and a cathode active material layer disposed on the cathode current collector and including a first surface, and a second surface opposite the first surface and adjacent to the cathode current collector, wherein the cathode active material layer includes a cathode active material including a dopant, and wherein a concentration gradient of the dopant decreases in a direction from the first surface to the second surface.

This application provides a lithium-nickel-manganese-based composite oxide material, where a K value of the lithium-nickel-manganese-based composite oxide material ranges from 1 to 2, and the K value is calculated based on the following formula: K=D.sub.v50/d.sub.v50, where d.sub.v50 is a volume median crystallite diameter of crystal particles of the lithium-nickel-manganese-based composite oxide material; and D.sub.v50 is a volume median particle diameter of the lithium-nickel-manganese-based composite oxide material.

This application provides a lithium-nickel-manganese-based composite oxide material, where a K value of the lithium-nickel-manganese-based composite oxide material ranges from 1 to 2, and the K value is calculated based on the following formula: K=D.sub.v50/d.sub.v50, where d.sub.v50 is a volume median crystallite diameter of crystal particles of the lithium-nickel-manganese-based composite oxide material; and D.sub.v50 is a volume median particle diameter of the lithium-nickel-manganese-based composite oxide material.

A positive electrode active material has a small difference in a crystal structure between the charged state and the discharged state. For example, the crystal structure and volume of the positive electrode active material, which has a layered rock-salt crystal structure in the discharged state and a pseudo-spinel crystal structure in the charged state at a high voltage of approximately 4.6 V, are less likely to be changed by charging and discharging as compared with those of a known positive electrode active material. In order to form the positive electrode active material having the pseudo-spinel crystal structure in the charged state, it is preferable that a halogen source such as a fluorine and a magnesium source be mixed with particles of a composite oxide containing lithium, a transition metal, and oxygen, which is synthesized in advance, and then the mixture be heated at an appropriate temperature for an appropriate time.

A cathode active material includes a lithium composite oxide having a crystal structure which belongs to a layered structure. The lithium composite oxide has a BET specific surface area of not less than 5 m.sup.2/g and not more than 10 m.sup.2/g. The lithium composite oxide has an average particle size of not less than 3 μm and not more than 30 μm. The lithium composite oxide, an average crystallite size calculated by an X-ray diffraction method is not less than 150 Å and not more than 350 Å.

Rechargeable lithium battery includes a negative electrode including a negative active material layer and a negative electrode functional layer disposed on the negative active material layer; a positive electrode including a positive active material; an electrolyte solution, wherein the negative electrode functional layer includes flake-shaped polyethylene particles, the electrolyte solution includes a lithium salt and a non-aqueous organic solvent, and the non-aqueous organic solvent includes about 60 volume % to about 80 volume % of a propionate-based solvent and about 20 volume % to about 40 volume % of a carbonate-based solvent.

A method for forming a sintered composition including providing a slurry precursor including a lithium-, sodium-, or magnesium-based compound; tape casting the slurry precursor to form a green tape; and sintering the green tape at a temperature in a range of 500° C. to 1350° C. for a time in a range of less than 60 min to form a sintered composition, such that the slurry precursor further includes a solvent and dispersant. The dispersant may include an amine compound, a carboxylic acid compound, or combinations, mixtures, or salts thereof.